Most of the systems of the body are formed by this stage, although the liver and lungs still have some way to develop. Your baby's immune (disease-fighting) system is still a work in progress too.
This week marks the beginning of the third trimester, and your antenatal classes should be starting soon. In most areas you will have a free local NHS class, as well as classes run by other organisations such as the National Childbirth Trust. The content of these classes can vary, but should cover important topics such as labour, breathing techniques and positions for giving birth. Some classes are just for women, but if dads can attend, it will help them prepare too.
Babies are born with immunity (protection) against diseases, which comes from their mother both in the womb and through breast milk. Not all vaccines have been declared safe to be given during pregnancy. It's best to have all vaccinations before you get pregnant. If you are already pregnant, try to avoid travelling to a country where you'll need vaccinating beforehand. If you can't avoid the trip, do get vaccinated because as a general rule, the disease will probably be more harmful to your baby than the vaccination.